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As insect wings develop, they form "crumpled up" in a very particular way. Unlike origami, there are no crisp folds. Then, at adulthood, the wings emerge and open up. Here is a cricket hindwing that I prepped from a juvenile, compared to an adult wing (from Turchyn & Popadić, FEVO 2024) 🧪

A fluorescent micrograph of a crumpled insect wing, with muscles and cuticle highlight in different colors. Scale bar of 200µm. The whole wing is about 1mm across.

A wild-type female hindwing from a cricket, mounted flat. The whole thing is maybe 10mm across.

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Yep fly larvae are baby flies that hatch from eggs. Those eggs have eggshells. Indeed, these arthropod eggshells evolutionarily pre-date amniote eggs with eggshells (like those of lizards, dinos, birds, echidnas, etc)

Those areas are fluid-filled during eggshell secretion (a liquid called hemolymph—mostly water). And then two more layers are added on top, covering everything including the cavities—"the roof network" & exochorion. Then, I suspect, the water evaporates from the laid egg if it's laid somewhere dry.

Yeah, it might be. In fact, fairly little is known about how insect eggshells get their fine-scale structure. But the idea of "spatial templating" is one of my favorite hypotheses.

Ya, you can think of the cells that build the insect eggshell as working like a 3D printer. The cells surround the yolk, secreting a bunch of protein layers onto it. Then those cells slough off and you're left with just the egg + eggshell. The eggshell is dead in the same way that mucus & teeth are.

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This is a different protein :) It's called Cp7Fc, which is only found in the eggshell. Very little is known about it. In this case, a copy of Cp7Fc has been fused to a fluorescent protein called "superfolder green fluorescent protein" (sfGFP). Unlike tubulin, Cp7Fc is secreted outside the cells.

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Seth Donoughe @donoughe.bsky.social · 04/08/2023

Geometric order at multiple scales. This is an optical slice into the eggshell of a fruit fly. Every dot is the cross-section of a tiny pillar holding up the "roof" that is the outer surface of the egg. The black polygons are cavities left where cellular interfaces used to be. 🧪

A fluorescent image of an insect eggshell. Polygons with black edges, each of which is filled with a quasi-orderly arrangement of tiny blobs. A scale bar that is approximately the width of one polygon is labeled "20 µm"

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You know those "veins" on the wings of insects? In some species, they join together with surprisingly complex mechanical linkages. This is an electron micrograph we captured of a vein joint from a damselfly. Note how the cuticle spikes allow more flexibility in one direction than the other. 🧪

An SEM of a vein joint from a damselfly. There is an horizontal cuticle strut, with two other struts meeting it perpendicularly. Where they meet, the other struts have spikes protruding towards the horizontal one.

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Seth Donoughe @donoughe.bsky.social · 02/08/2023

A larva of the "lesser house fly" Fannia canicularis, illustrated in the Manual of Nearctic Diptera. This book has astonishingly detailed and loving drawings of larvae. 🧪

A pen and ink drawing of the "lesser house fly" Fannia canicularis, illustrated in the Manual of Nearctic Diptera. The surface has detailed textural features.

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Seth Donoughe @donoughe.bsky.social · 13/07/2023

Could I join the list? I am a biologist who makes SciArt within and apart from my research. Thanks for curating an excellent feed. (I love the guidelines, btw)

Seth Donoughe @donoughe.bsky.social · 13/07/2023

~Embryo gymnastics~ In some insect species, the developing embryo does half of a backwards somersault (a movement called "katatrepsis"). Kozo Miyakawa captured this process in a dragonfly in a 1987 paper w/ tons of pen & ink illustrations. 🧪 (freely available: aesj.co-site.jp/raiejp.html)

A series of 7 stages of dragonfly embryogenesis, showing the embryo re-orient itself by doing a backwards flip.

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Nice! This is the first I've heard of him. Just found some of his amphipod drawings online. These are lovely.

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The old descriptive embryology papers had some gems of hand-drawn illustration. These are drawings of the developing embryo of a cabbage white butterfly (Pieris rapae), a species that is often an unwelcome muncher of your kale and bok choy plants. by L.E.S. Eastham (Phil. Trans. Roy. Soc., 1930) 🧪

Four pen and ink drawings of insect embryos. At these stages, the embryos have the shape of a blobby worm with constrictions between each body segment.

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strong agree. i come across deeply unsettling forms at the microscope more often than i would have anticipated. it's spooky down there.

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